A group of communist guerillas in Cambodia during the late 20th century, led by Pol Pot, that gained control of Cambodia after the withdrawal of American troops from the Vietnam War. The initiated a reign of terror, killing over a million people to remove all western influence from the country. This gross violation of human rights ended when Vietnam invaded and occupied the country in 1979. In the 1990s, the United Nations negotiated a peace settlement, and began the democratic process in Cambodia.